As substrates for information recording media, particularly for magnetic disks, glass substrates are widely used, and, for example, a glass containing, as represented by mass %, from 47 to 60% of SiO2, from 8 to 20% of Al2O3, from 2 to 8% of Na2O, from 1 to 15% of K2O, from 1 to 6% of TiO2 and from 1 to 5% of ZrO2 has been proposed.    Patent Document 1: WO 08/117,758